d. To thicken a grout, the volume of the cement solids, in cubic feet
(one~half the number of sacks of cement in the grout) is subtracted from the
cubic feet of grout to obtain the volume of water in the grout. Enough cement
is added to have the desired water-cement ratio with this volume of water.
It is preferable to add only whole sacks of cement.
e. Most chemical grouts are liquid grouts consisting of mixtures of liq-
uids, and the consistency is usually not changed. The application and pene-
tration of these grouts depend upon the gel or setting time, which can be
regulated as required. As previously noted, chemical grouts vary widely in
under the direction of personnel trained in the use of the particular chemi-
cals being used.
PRESSURE OF GROUT COLUMN. As in changing grout from one mix to
another, the quickest way to determine the pressure exerted by a column of
grout is by using a chart. In case a chart similar to figure 4 (main text) is
not at hand, the pressure in pounds per square inch exerted by a 1-ft column
of any grout can be found by dividing the weight of a cubic foot of the grout
by 144 (the number of square inches in a square foot). For portland-cement
grout with no fillers or admixtures , it is necessary to know that a cubic foot
of water weighs 62.4 lb and a sack of cement weighs 94 lb. Thus, for 2:1
grout a one-sack batch of grout contains 124.8 lb of water and 94 lb of ce-
ment for a total weight of 218.8 lb. Since a one-sack batch of 2:1 grout
makes 2.5 cu ft, 218.8 lb must be divided by 2.5 to obtain the weight of 1 cu ft
of the grout. Then 1 cu ft of 2:1 grout weighs 87.5 lb and exerts a pressure